#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netdb.h>
#include <setjmp.h>
#include <errno.h>

#include <linux/if.h>

#define PACKET_SIZE     4096
#define MAX_WAIT_TIME   5
#define MAX_NO_PACKETS  100000

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
static int sockfd,datalen=56;
static int nsend=0,nreceived=0;
static struct sockaddr_in dest_addr;
pid_t pid;
struct sockaddr_in from;
struct timeval tvrecv;

pthread_t send_thread;

void statistics(int signo);
unsigned short cal_chksum(unsigned short *addr,int len);
static int pack(int pack_no);
void send_packet(void);
void recv_packet(void);
int unpack(char *buf,int len);
void tv_sub(struct timeval *out,struct timeval *in);
int stop = 0;
void statistics(int signo){
    stop = 1;
    printf("/n--------------------PING statistics-------------------/n");
    printf("%d packets transmitted, %d received , %%%d lost/n",nsend,nreceived,
           (nsend-nreceived)/nsend*100);
    pthread_join(send_thread, NULL);
    close(sockfd);
    exit(1);
}

/*校验和算法*/
unsigned short cal_chksum(unsigned short *addr,int len){
    int nleft=len;
    int sum=0;
    unsigned short *w=addr;
    unsigned short answer=0;

/*把ICMP报头二进制数据以2字节为单位累加起来*/
    while(nleft>1){
        sum+=*w++;
        nleft-=2;
    }
/*若ICMP报头为奇数个字节，会剩下最后一字节。把最后一个字节视为一个2字节数据的高字节，这个2字节数据的低字节为0，继续累加*/
    if( nleft==1){
        *(unsigned char *)(&answer)=*(unsigned char *)w;
        sum+=answer;
    }
    sum=(sum>>16)+(sum&0xffff);
    sum+=(sum>>16);
    answer=~sum;
    return answer;
}

/*设置ICMP报头*/
static int pack(int pack_no){
    int i,packsize;
    struct icmp *icmp;
    struct timeval *tval;

    icmp=(struct icmp*)sendpacket;
    icmp->icmp_type=ICMP_ECHO;
    icmp->icmp_code=0;
    icmp->icmp_cksum=0;
    icmp->icmp_seq=pack_no;
    icmp->icmp_id=pid;
    packsize=8+datalen;
    tval= (struct timeval *)icmp->icmp_data;
    gettimeofday(tval,NULL);    /*记录发送时间*/
    icmp->icmp_cksum=cal_chksum( (unsigned short *)icmp,packsize); /*校验算法*/

    return packsize;
}

/*发送三个ICMP报文*/
void send_packet(){
    int packetsize;
    while((nsend<MAX_NO_PACKETS) &&
          (!stop)){
        nsend++;
        packetsize=pack(nsend); /*设置ICMP报头*/
        if( sendto(sockfd,sendpacket,packetsize,0,
                   (struct sockaddr *)&dest_addr,sizeof(dest_addr) )<0 ){
            perror("sendto error");
            continue;
        }
        sleep(1); /*每隔一秒发送一个ICMP报文*/
    }
}

/*接收所有ICMP报文*/
void recv_packet(){
    int n,fromlen;
    extern int errno;
    signal(SIGALRM,statistics);
    fromlen=sizeof(from);
    while((nreceived<MAX_NO_PACKETS) &&
          (!stop)){
        alarm(MAX_WAIT_TIME);
        if( (n=recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,
                        (struct sockaddr *)&from,&fromlen)) <0){
            if(errno==EINTR){
                continue;
            }
            perror("recvfrom error");
            continue;
        }
        gettimeofday(&tvrecv,NULL); /*记录接收时间*/
        if(unpack(recvpacket,n)==-1){
            continue;
        }
        nreceived++;
    }

}
/*剥去ICMP报头*/
int unpack(char *buf,int len){
    int i,iphdrlen;
    struct ip *ip;
    struct icmp *icmp;
    struct timeval *tvsend;
    double rtt;

    ip=(struct ip *)buf;
    iphdrlen=ip->ip_hl<<2;    /*求ip报头长度,即ip报头的长度标志乘4*/
    icmp=(struct icmp *)(buf+iphdrlen); /*越过ip报头,指向ICMP报头*/
    len-=iphdrlen;            /*ICMP报头及ICMP数据报的总长度*/
    if( len<8){                /*小于ICMP报头长度则不合理*/
        printf("ICMP packets/'s length is less than 8/n");
        return -1;
    }
/*确保所接收的是我所发的的ICMP的回应*/
    if ((icmp->icmp_type==ICMP_ECHOREPLY) && (icmp->icmp_id==pid) ){
        tvsend=(struct timeval *)icmp->icmp_data;
        tv_sub(&tvrecv,tvsend); /*接收和发送的时间差*/
        rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000; /*以毫秒为单位计算rtt*/
/*显示相关信息*/
        printf("%d byte from %s: icmp_seq=%u ttl=%d rtt=%.3f ms/n",
               len,
               inet_ntoa(from.sin_addr),
               icmp->icmp_seq,
               ip->ip_ttl,
               rtt);
    }else{
        return -1;
    }
}

int main(int argc,char *argv[]){
    struct hostent *host;
    struct protoent *protocol;
    unsigned long inaddr=0l;
    int waittime=MAX_WAIT_TIME;
    int size=50*1024;
    struct ifreq interface;

    if(argc<3){
        printf("usage:%s hostname/IP address/n",argv[0]);
        exit(1);
    }

    if( (protocol=getprotobyname("icmp") )==NULL){
        perror("getprotobyname");
        exit(1);
    }

   /*生成使用ICMP的原始套接字,这种套接字只有root才能生成*/
    if( (sockfd=socket(AF_INET,SOCK_RAW,protocol->p_proto) )<0){
        perror("socket error");
        exit(1);
    }

    printf("ifname:%s/n",argv[2]);

    strncpy(interface.ifr_ifrn.ifrn_name, argv[2], IFNAMSIZ);

    if (setsockopt(sockfd, SOL_SOCKET, SO_BINDTODEVICE, (char *)&interface, sizeof(interface)) < 0) {
        printf("SO_BINDTODEVICE failed");
        exit(1);
    }

/* 回收root权限,设置当前用户权限*/
    setuid(getuid());
/*扩大套接字接收缓冲区到50K这样做主要为了减小接收缓冲区溢出的
  的可能性,若无意中ping一个广播地址或多播地址,将会引来大量应答*/
    setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size) );
    bzero(&dest_addr,sizeof(dest_addr));
    dest_addr.sin_family=AF_INET;
/*判断是主机名还是ip地址*/
    if( inaddr=inet_addr(argv[1])==INADDR_NONE){
        if((host=gethostbyname(argv[1]) )==NULL){ /*是主机名*/
            perror("gethostbyname error");
            exit(1);
        }
        memcpy( (char *)&dest_addr.sin_addr,host->h_addr,host->h_length);
    }else{    /*是ip地址*/
        struct in_addr ip_addr;
        ip_addr.s_addr = inet_addr(argv[1]);
        dest_addr.sin_addr  = ip_addr;
    }
/*获取main的进程id,用于设置ICMP的标志符*/
    pid=getpid();
    printf("PING %s(%s): %d bytes data in ICMP packets./n",argv[1],
           inet_ntoa(dest_addr.sin_addr),datalen);
    signal(SIGTERM, statistics);
    signal(SIGINT, statistics);
    signal(SIGABRT, statistics);
    signal(SIGQUIT, statistics);
    signal(SIGKILL, statistics);
/*发送所有ICMP报文*/
    if (pthread_create(&send_thread, NULL, (void*)send_packet, NULL) != 0) {
        printf("Create send thread failed./n");
        exit(1);
    }
    recv_packet();
//statistics(SIGALRM); /*进行统计*/

    return 0;

}

/*两个timeval结构相减*/
void tv_sub(struct timeval *out,struct timeval *in){
    if( (out->tv_usec-=in->tv_usec)<0){
        --out->tv_sec;
        out->tv_usec+=1000000;
    }
    out->tv_sec-=in->tv_sec;
}

